I bought a 95 SLS last month with a Northstar engine. The car had 102K when I bought it and it now has 104K.
It runs great, but I am unsure as to what maintenance has been done. That said, I want to start with tuning the engine up, but I don't know what a tune up on a Northstar consists of and whether or not I need to take the car to the dealer to have it done.
Another question is that I know it takes quite a bit of money to run a Northstar Cadillac, but I wanted to get an idea of where that money is likely to go besides on premium petrol.

I don't know if it is just me but my car rides a little hard for a Cadillac, is that common in 92-97 Sevilles? It rides good though and it does not shake at speed or bottom out over bumps, but it rides a little harder than I expected a large Cadillac to ride.

My car has a new exhaust system, but the exhaust note is quite gruff than I expect in a Cadillac, sometimes I don't know if I am driving a Seville or a Camaro. It does sound good, and I guess it is a good trade-of for the performance I get.

JSMeloche

07-08-04, 11:49 AM

Here is one of my previous post on tune up

Good morning
This is a post to reassure all of you who are afraid to do a tune up on the North* engine. It is very easy! i did mine this weekend in 2 hours (95 STS 85k). I changed the plug, plug wire, fuel filter and air filter.

Just go slowly.
These are the step i followed to change the plugs and wire.
#1 remove the engine cover (open the hood first lol)
#2 remove the strut brace. This is easy and gives you a lot of place to work
#3 remove the coil pack. 2 bolts on the back and 2 bolts on the side (10mm). This will give you easy access to all four rear spark plugs
#4 remove plug wire and change the plug. Do the plug one at a time. You should not have any problem removing the plug in the back. Use a spark plug socket, the one with the rubber to hold the plug in place and a extension.
#5 change the wire one at a time making sure you put it back on the correct terminal. This is pretty foolproof. The number of the cylinder is labeled on the block and the terminal is labeled on the coilpack AND in some case it is labeled on the wire as well.
#6 Put everyting back in place

For the fuel filter is is on the driver side of the car underneath the rear door.
#1 Remove the fuel pump fuse and run the car until it stalls. This will remove most of the pressure from the fuel line.
#2 Jack the car.
#3 Locate the fuel filter and remove it. I used a screwdriver to break the plastic thingy that hold it there but im pretty sure there is a better way to do it.
#4 Put the new filter in place using the new plastic retainer
#5 Dont forget to put the fuel pump fuse back!

145$ CAN for the wires
105$ CAN for the spark plugs
12$ CAN for a fuel filter
100$ CAN K&N 33-2086 this is a direct fit for the STS even tough it is not listed on K&N site.

The dealer wanted over 800$ to do all this!!! can you beleive it! I did all this in about 2 hours. Now the STS is even smoother at idle and scream at WOT.

As for the ruff ride consider that the STS is kind of a "hot rod" Cadillac. Mine rides a little ruff too but an STS needs to handle dude ;) You dont want to take a turn @ 120mph+ with the "boat" kind of suspension. you want someting that is responsive!

Ranger

07-08-04, 08:59 PM

I would say if it ain't broke, don't fix it. The dual platinum tipped plugs will last damn near forever as well as the wires. If it isn't missing, don't mess with it. If you do, use OEM parts. I have heard of many people having problems after a tune up with aftermarket plugs or wires.
The cooling system is more important. It should have green coolant and needs to be changed every 2 years. Don't forget to add the GM sealant tabs or 2 tubes of "Bars Leak Gold" (same thing).
Unless you are going to race it, save your money and run 87 octane. The Northstar has a knock sensor that will retard the spark as neccassary if it detects spark knock. You probably won't even notice the difference in performance. I don't.
Oh yeah, don't forget to give it some tender loving WOT once a week. Just plant your right foot firmly on the floor and hold it there til it shifts. Yup, red line it. That will clean out the cumbustion chambers. The Northstar has a tendency to carbon up if babied. If it gets carboned up you will hear "cold carbon rap" when you start it. Sounds a lot like a collapsed lifter. That is the piston contacting the carbon in the cylinder head causing piston slap. No need to worry. Just take her out and whoop her. She'll be fine and love you for it.
Other than that, just change oil per the OLI (oil life indicator) and enjoy it.
I have not found the Nortstar any more expensive than any other engine to run. Now a head gasket problem is another story so keep up with the coolant changes.

knifeparty420

07-08-04, 09:35 PM

wow that cold carbon rap thing is crazy. now that I think about I kinda do baby my Caddy. I thought that knocking noise when started was something to do with the pulleys the belt goes on knocking. thanks and I can't wait for WOT.

Ranger

07-08-04, 10:34 PM

When you whoop it, glance in the mirror. You'll probably see a lot of soot, rust & crap in the air. When you don't see that anymore, she's clean and the cold carbon rap will be gone.If it's really carboned up it may take more than one WOT application. Not a problem, they are fun ;)

wow that cold carbon rap thing is crazy. now that I think about I kinda do baby my Caddy. I thought that knocking noise when started was something to do with the pulleys the belt goes on knocking. thanks and I can't wait for WOT.

caddywhizkid

07-09-04, 01:11 AM

Nothing to "tune up" really. If the engine is running fine leave it alone. If it develops a miss then possibly inspect/replace the spark plugs/wires.

With those miles I would replace the main serpentine accessory belt and specifically the belt at the other end of the engine that drives the water pump. Neither owe you a dime after 100,000 miles. :p Make sure the water pump drive belt tensioner is operating correctly and not frozen due to corrosion. Exercise it when you replace the small belt at the water pump and lube the pivot point.

Clean the throttle body bore to eliminate and sticky throttle feel and/or idle speed control issues. Just hold the throttle open and spray the bore with carb cleaner and scrub with an old toothbrush. Disconnect the battery negative cable for 30 seconds to reset the idle speed learn offsets for the clean throttle body.

Service the coolant system. This is the single most important thing to insure long life of a Northstar engine. The green silicated coolant needs to be replaced every 2-3 years/24-32 K miles to maintain an adequate concentration of corrosion inhibitors in the coolant. Replace the coolant with fresh 50/50 coolant/distilled water and add the coolant supplement to the radiator hose as described.

I bought a 95 SLS last month with a Northstar engine. The car had 102K when I bought it and it now has 104K.
It runs great, but I am unsure as to what maintenance has been done. That said, I want to start with tuning the engine up, but I don't know what a tune up on a Northstar consists of and whether or not I need to take the car to the dealer to have it done.
Another question is that I know it takes quite a bit of money to run a Northstar Cadillac, but I wanted to get an idea of where that money is likely to go besides on premium petrol.

I don't know if it is just me but my car rides a little hard for a Cadillac, is that common in 92-97 Sevilles? It rides good though and it does not shake at speed or bottom out over bumps, but it rides a little harder than I expected a large Cadillac to ride.

My car has a new exhaust system, but the exhaust note is quite gruff than I expect in a Cadillac, sometimes I don't know if I am driving a Seville or a Camaro. It does sound good, and I guess it is a good trade-of for the performance I get.

gserep1

08-09-04, 10:34 PM

My sister has a 98 STS...isn't the coolant ORANGE? Does it use the DEX-COOL? Sounds like a coolant change is in the plans, plus some radiator supplement or bars' leak...(never had a car that needed this stuff).

This is our first all aluminum engine..NOW I have a 99 Lexus GS400 with 4.0L V8 aluminum engine too. I use this as my personal daily driver, but have to take care of the STS now that Dad's gone.

Thanks for all the info anyone can give me!
GSEREP1

Kerb

08-09-04, 11:27 PM

Yea, I just changed and flushed mine with the orange. Any problems using the orange?

gserep1

08-09-04, 11:36 PM

Did you use the coolant supplements in the top radiator hose? Did you just do a quick drain, or did you do a complete flush by draining the block?

I am doing the coolant on my 98 STS on Friday this week.

Thanks so much!
GSEREP1

Ranger

08-10-04, 01:33 PM

Orange (Dex-cool) was used starting in '96. If it's a '98 it is due. Be sure to put the tabs in the radiator hose, not the surge tank. There is really no need to flush. The theory is that flushing (probably with a garden hose) will just add contaminents (calcium, lime etc) from the water to the cooling system. Just drain and refill with 50/50 distilled water/Dex-cool.

gserep1

08-10-04, 07:18 PM

OUTSTANDING! Thanks for the quick response. I will do just as you recommend. Is the GM stuff better than the Bars' leak you get at auto parts stores?

On all my other cars I change colant each year, and so far, I have never had a clogged radiator, or needed to change a thermostat or water pump. I don't suppose I need to think about changing thermostats do I? What did you do?

If you take care of the cooling systems, they will take care of you. NUFF SAID!

Thanks again!
GSEREP1

eagleworks4u

11-18-04, 12:05 PM

Is dex cool recommended for 94 northstars or is reg 50/50 mix ok??

chazglenn3

11-18-04, 01:03 PM

The recommendation is to use the same as the factory original fill. In the case of the 94 Northstar it was the green coolant.

thatwolfofmine

04-12-07, 04:53 PM

I need help. My '96 Caddy DeVille has a bad overheating problem. It supposedly does not have blown headgaskets. What else do I need to look for?

Ranger

04-12-07, 06:18 PM

Use the search button at the top of the page and do a search for overheating. There are many things that could cause it and all have been discussed in detail before. You should find a lot to read.

fposada

07-02-08, 05:06 PM

I WANT TO CHANGE THE SPARK PLUGS ON MY CATERA BUT CAN'T SEE WHERE THEY ARE LOCATED... :banghead:
DOES ANYONE HAVE A DIAGRAM AVAILABLE OF WHERE THE SPARK PLUGS ARE EXACTLY LOCATED ON A 2001 CATERA?

Submariner409

07-02-08, 05:09 PM

cAPS lOCK............

Catera threads ^^^^^ up there.

mythy

03-30-10, 07:47 PM

Hey guys what sensor needs to be cleaned if the idle is irregular at well... Idle? It goes from 800rpms to 400 and surges. I cleaned the throttle body did the plugs and wires as well. Running nice synthetic oil and got a good air filter on.

Ranger

03-30-10, 09:36 PM

Maybe the IAC valve on the side of the TB or a vacuum leak. Cleaning the TB should have cleaned the IAC valve opening.

tonecapone

05-08-12, 09:21 PM

What is the result from putting the Delco tabs in the tank?

Ranger

05-08-12, 10:21 PM

The tank is a low flow area. They will probably just sit there and clog up the tank. If you are going to use them, put them in one of the radiator hoses.

Omerus

08-11-12, 07:03 PM

I too was looking up maintenance suggestions for the Northstar and you hit the nail on the head for my car. It got regular tune-ups twice a year before I bought it and it runs like a dream but developed a warning light for coolant. I parked it till my mechanic could inspect it. Stale coolant is an overlooked area. . For $300 they fixed the housing and flushed the system with new coolant. The car is running like a dream.
Maintenance lessons from 30 years ago are probably not relevant anymore. I am learning that.

Submariner409

08-11-12, 08:42 PM

Stale coolant is an overlooked area. . For $300 they fixed the housing and flushed the system with new coolant. The car is running like a dream.
Maintenance lessons from 30 years ago are probably not relevant anymore. I am learning that.

One reason that "stale coolant" is an overlooked area is because new car owner/drivers are conditioned to believe their car is going to turn on a "HELP ME !!! light before it blows up. Wrong.

Ranger

08-11-12, 10:29 PM

I too was looking up maintenance suggestions for the Northstar and you hit the nail on the head for my car. It got regular tune-ups twice a year before I bought it.
Maintenance lessons from 30 years ago are probably not relevant anymore. I am learning that.
Boy, talk about "old school". Yes, some things are no longer relevant.

ELDO GUY

08-14-12, 04:51 PM

I think you can save your self a lot of time and energy and possibly money . Just start out with the block test and get it over with. If it passes then you can look for the easier less expensive stuff. My car never overheated, but it still had headgasket failure! I wasted a lot of time looking/hoping for the less expensive repair!

CadillacLuke24

09-13-12, 11:27 PM

There's a spark plug tutorial in the tech tips section, but some of us (like me) like pictures because they help show where stuff is, and sometimes ya just can't beat a picture. So here goes.

As far as tools go, a basic socket set (metric), a spark plug socket lined with rubber (INVALUABLE) and anti-seize compound is all that is needed. You may want some electrical tape.

Parts include 8 AC-Delco 41-950 plugs and I used the 748J wire set. Length is near factory specs, which is nice.

Pop the hood :lol:

Remove the strut brace bar that stretches across the back of the engine bay. I believe the socket is 13mm This gives a lot of space for the rear bank when you get to it:

After getting the beautay cover off, you'll want to remove the plug wires from the ignition coils that sit above the rear bank. Easy, just pop the connections off. The same goes for the plug boots. I left those in the plug holes as to avoid getting stuff in the plug holes. Take note of plug wire routing so you know what goes where when you button things back up. This is where that electrical tape came in handy for me.

Next, you'll want to remove the ignition coils. All of them are mounted on a metal plate. Four screws, two on the front and two on the rear, hold it down. 10mm socket. There's also 2 electrical connections per side on the left and right sides of the ignition coils. Make sure those come off when you remove the coils. More importantly, make sure they are all plugged in when you go to test your repair. Ask me how I know.

Since the plug connections are labeled on the coils, I did all of the plugs an once. Check yours before starting to determine if you can do the same.

The front bank is easy. They take some oomph to get loose at first, but all mine came out with good threads and the threads in the block were good.

With the coils and the strut brace out of the way, the rear bank is a BREEZE. If you're a vertically challenged individual, a stool may be handy. All I'm saying :duck: is that I'm 6'1 and I had no trouble getting to the rear bank. That being said, there was something in the way on the left side. Not sure what it is (HINT HINT :D) but one 10mm bolt holds it down.

Coat the first three threads with anti-seize, I've heard that's more than enough. Don't be gun-shy when reinstalling plugs, just go nice and slow. Center the plug socket in the hole and the plugs pretty much center themselves. Stop right after the plugs first really snug up. That way if you ever do this again it won't be a pain in the butt (The anti-seize helps too :D).

The old plugs have some oil near the thread base. O-ring seepage from the heads, and perfectly NORMAL. Carboned-up electrodes, also normal. Another typical old plug condition is the carbon tracking, apparently oil, near the base of the white part (I know, technical :D). The plug wires usually have this as well (from what I've heard, and my plug boots smelled JUST like motor oil) so it's a good idea to change the wires too, even though it may seem excessive.